package com.gao.readandwrite;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.BlockingDeque;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 * ReadWriteLock
 * 独占锁（写锁）：一次只能被一个线程占有
 * 共享锁（读锁）：多个线程可以同时占有
 * 读-读 可以共存
 * 读-写 不能共存
 * 写-写 不能共存
 */
public class ReadWriteLockDemo {

    public static void main(String[] args) {
//        MyCache myCache = new MyCache();
        MyCacheLock myCache = new MyCacheLock();
//        写入
        for (int i = 1; i <= 30; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.put(temp + "", temp + "");
            }, String.valueOf(i)).start();
        }
//        读取
        for (int i = 1; i < 30; i++) {
            final int temp = i;
            new Thread(() -> {
                myCache.get(temp + "");
            }, String.valueOf(i)).start();
        }
    }
}

/**
 * 自定义缓存
 */
class MyCache{
    private volatile Map<String, Object> map = new HashMap<>();

    public void put(String key, Object value){
        System.out.println(Thread.currentThread().getName() + "\t 正在写入：" + key);
        map.put(key, value);
        System.out.println(Thread.currentThread().getName() + "\t 写入完成");
    }
    public void get(String key){
        System.out.println(Thread.currentThread().getName() + "\t 正在读取");
        Object result = map.get(key);
        System.out.println(Thread.currentThread().getName() + "\t 读取完成：" + result);
    }
}

/**
 * 自定义缓存 读写锁
 */
class MyCacheLock {
    private volatile Map<String, Object> map = new HashMap<>();
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

//    存，写入的时候，只希望同时只有一个线程写
    public void put(String key, Object value) {
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + "\t 正在写入：" + key);
            // 模拟网络延迟
            try {
                TimeUnit.MILLISECONDS.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            map.put(key, value);
            System.out.println(Thread.currentThread().getName() + "\t 写入完成");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.writeLock().unlock();
        }
    }
//    取，读，所有人都可以读！
    public void get(String key) {
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName() + "\t 正在读取");
            // 模拟网络延迟
            try {
                TimeUnit.MILLISECONDS.sleep(300);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            Object result = map.get(key);
            System.out.println(Thread.currentThread().getName() + "\t 读取完成：" + result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            readWriteLock.readLock().unlock();
        }
    }
}
